If you are using the WordPress Yoast SEO Search Console, you might wonder what the soft 404 means, the SEO search console shows all the Google search crawl errors and issues related to your site.
Just because a page says 404, doesn’t mean it’s returning a 404 status code. A ‘Soft 404’ error occurs when a non-existent page (a page that has been deleted/removed) displays a ‘page not found’ message to anyone trying to access it but fails to return an HTTP 404 status code.
They can also occur when the non-existent page redirects users to an irrelevant page, such as the homepage, instead of returning an HTTP404 status code. The important thing to remember here is that the content of a web page is entirely unrelated to the HTTP response returned by the server.
Let’s say http://example.com/happy/ was displaying a 404 page to the user trying to access it, but when checking the response code using an HTTP status code checker, it returned an HTTP 200 response. This is a prime example of a Soft 404 error, as the HTTP response code is indicating to search engine robots that the page exists and should be crawled. However, there is no content on the page that’s returned by the server.
You can run your 404 error URL through an HTTP status code checker httpstatus.io, to assess which status codes are returned. It gives you an insight into what is going on.
Another tool that you can use to check the HTTP response codes returned by your webpages is Tools I Seek.
Another great tool is the redirect tracker, to see where your redirects are going, it can also be used as a phishing tool by you, to check to shorten URLs that you receive in your emails.
That is it
You can also read more in this article Do 404 errors affect SEO?
You may also check out these resources for WordPress Yoast SEO.